Mattress having a two-part core with stiffness increasing toward the center

Abstract: The invention relates to a mattress having a core formed from foamed material. The core comprises a core part (3) and a number of edge parts (4), the core part (3) in longitudinal section of the mattress having a gradually increasing thickness from the two ends in the direction of the center. The core part (3) is manufactured from a material having a greater stiffness than the edge parts (4) and the core formed by the core part (3) with edge parts (4) provided thereon is substantially block-shaped, the arrangement being such that the stiffness of the mattress gradually increases in the direction of the center.

Description: The invention relates to a mattress according to the preamble of claim 1. Normally, mattresses have a core formed from foamed material, such as, for instance, foam rubber or latex rubber, are substantially block-shaped, and have a constant stiffness distributed over the surface. During use, the mattress under the body of the user will be compressed locally, causing a deformation of the mattress. When the user is in a normal lying position, his hips will be located approximately at the center of the mattress, his head near the head end and his feet near the foot end. Hence, in that position, the larger part of his weight will be borne by the center portion of the mattress, and consequently, the greatest compression will occur at that location. At the head and foot ends, this compression will clearly be smaller. The deformations of the mattress that occur have an adverse effect on the durability of the mattress and on the outward appearance thereof, in particular during use, but due to repeated use, permanent deformations will occur as well. Moreover, the deformations occurring have an adverse effect on the body support and hence on the practical comfort of the mattress. Due to the greater compression of the mattress, a hollow is formed in the center portion of the mattress, as a consequence of which the user's head and feet are pushed upward relative to his hips and his back is forced into a bent, unfavourable position. The mattress described in the preamble, which is known from FR-A-2 002 306 overcomes the disadvantages of the conventional mattresses. The known mattress comprises a first part and a second part. The first part can be considered to be a core part but forms the top of the mattress. The second part forms the bottom of the mattress. The thickness of the core part increases in the longitudinal direction from the longitudinal ends towards the longitudinal center of the mattress. The object of the invention is to provide a mattress having the advantages of the mattress known from FR-A-2 002 306 which can be used on both sides. According to the invention, the mattress described in the preamble is characterized by the features mentioned in the characterizing portion of claim 1. Such a mattress is turnable, as a result of which the mattress is simple in use and the service life can be influenced positively, because the two sides of the mattress will periodically be loaded mechanically and thermally, while the body-supporting characteristics on both sides of the mattress are equal. The mattress according to the invention has in the center portion a greater stiffness than near the head and foot ends. Due to this greater stiffness, the difference in compression between the center portion and the head and foot ends of the mattress will be optimum, as a result of which hollow formation in the mattress, and hence an uncomfortable lying position for the user, is prevented, the durability of the mattress is increased and the outward appearance is influenced positively, both during and after repeated use. Because the core part is of a diamond-shaped design, the thickness thereof changes gradually from the two ends in the direction of the center, while the thickness of the edge parts located on both sides of the center above and below the core part increases in opposite direction. As the material of the edge parts has a lower stiffness than the material of the core part, the stiffness of the entire core also gradually increases from the two ends in the direction of the center, while the difference between the stiffness of the core part and of the edge parts may be relatively small, which benefits the supporting characteristics of the mattress. As the core part defines at least a part of the top and bottom face of the core, or at any rate touches it, and is located centrally between these faces, the edge parts lying opposite one another are similar in form and complementary, so that they can readily be obtained, with hardly any waste, from an approximately rectangular block, and the core has a constructively simple construction. Preferably, of the core of the mattress according to the invention, the proportion of the stiffness near the foot end to the stiffness near the center and near the head end is as at least 3:4:3, and in a particularly advantageous embodiment as 1:5:3. This provides a practically optimum distribution of the occurent reactive forces when the mattress is used by a lying user, as a result of which a particularly favourable pattern of compression of the core of the mattress occurs. To explain the invention, a number of exemplary embodiments of the mattress will be described hereinafter, with reference to the accompanying drawing. In this drawing: Fig. 1 shows a mattress according to the invention in longitudinal section; and Fig. 2 shows a mattress according to the invention in a further embodiment. The mattress as shown in the drawing consists of a core 101, 201, manufactured from foamed material, such as foam rubber or latex rubber, and a mattress cover 102, 202, with the possible inclusion of different intermediate layers, known per se and not shown in the drawing, between the core and the cover. The core 101, 201 comprises a core part 103, 203 and a number of edge parts 104, 204. The core 101, 201 is substantially block-shaped. Fig. 1 shows an embodiment of the mattress whose core part 103 is of a diamond-shaped design and located centrally relative to the two lying surfaces 106. Each obtuse angle 107 of the core part 103 contacts a lying surface 106 of the core 101, while each acute angle 113 of the core part 103 is located near one of the ends 108 of the core 103. The edge parts 104 have a trapezoidal section, comprising two right angles 111. In each case, the part 108' located between the right angles 111 defines half of the relevant end 108. From the two right angles 111, abutting against each other, of the edge parts 104 at one end 108 of the core 103, a contact face 112 extends between the two relevant edge parts 104 tot the adjacent acute angle 113 of the core part 103. As a result, a confectioning edge 114 is formed along the two ends 108, on which the cover 2 can simply be fixed. The edge parts 104 are at least identical two by two (the edge parts opposite each other in vertical direction on both sides of the core part 103), and can be obtained from a substantially rectangular block without waste and in one cutting operation. The core part 103 may be manufactured from one piece, but may also be composed of two or four identical, triangular parts. This embodiment of the mattress according to the invention has the advantage that the stiffness thereof increases linearly from the two ends 108 in the direction of the center, yielding a proper supporting characteristic, while the mattress has a simple construction and can moreover be used on two sides. In the exemplary embodiment given, the obtuse angles 107 of the core part 103 are positioned in the center of the mattress, but it is also possible to construct the core part not as a true diamond form, but kite-shaped, so that the part of the mattress having the greatest stiffness is located off-center. In this manner, the supporting characteristic can be adapted such that the maximum reactive force is shifted more or less in the direction of the head end or, by contrast, the foot end. In particular when the core part 103 is composed of several parts, the apices 107 of the diamond form can moreover be arranged so as to be shifted in longitudinal direction relative to one another. Fig. 2 shows an embodiment of the mattress whose core part 203 is constructed with an approximately bell-shaped top and bottom face 210 and is located centrally relative to the two lying surfaces 206. Each apex 207 of the core part 203 forms a part of a lying surface 206 of the core 201, while each thin end 213 of the core part 203 lies near one of the ends 208 of the core 20. The edge parts 204 have a section such that they on the one hand fittingly abut against the core part surface 210, and on the other, together with the apices 207 of the core part 203, constitute the lying surfaces 206 and the two ends 208 of the mattress core 201. At the two ends 208 of the core 201, two edge parts 204 practically abut against one another by a face 212, and form a confectioning edge 214. This embodiment of the mattress according to the invention has the advantage that the stiffness gradually increases from the two ends 208 in the direction of the center, the increase being at least partly progressive, as a result of which the supporting characteristic is excellently adapted to the weight distribution of the body of the user. For different users, the contour of the core part can simply be adapted to optimise the stiffness distribution and, accordingly, the supporting characteristic individually. Obviously, in this embodiment, too, it applies that the position of the maximum stiffness can be varied at will, by displacing the apices relative to each other and/or the center of the mattress.

Claims: A mattress having a core (101, 201) formed from foamed material, the core comprising a first part (103, 203) being a core part (103, 203) and at least one second part (104, 204), the core part (103, 203) having a thickness which, seen in longitudinal section of the mattress, gradually increases from the two longitudinal ends (108, 208) in the direction of the center, the core part being manufactured from a material having a greater stiffness than the at least one second part (104, 204), the core (101, 201) formed by the core part (103, 203) and the at least one second part (104, 204) being substantially block-shaped, the arrangement being such that the stiffness of the mattress gradually increases in the direction of the center, characterized in that, the at least one second part comprises at least two edge parts (104, 204), the core part (103, 203) being substantially diamond-shaped and being located centrally between the edge parts (104, 204) relative to the top and bottom faces of the core (101, 201), such that the mattress can be used on two sides. A mattress according to claim 1, characterized in that the core part (103, 203) defines at least a part of the top and/or bottom face of the core (101, 201). A mattress according to any one of the preceding claims, characterized in that edge parts (104, 204) located near one end of the core (101, 201) on both sides thereof, abut against one another by a contact face (112, 212). A mattress according to any one of the preceding claims, characterized in that the core part (103, 203) is glued together with the edge parts (104, 204). A mattress according to any one of the preceding claims, characterized in that the stiffness of the mattress increases linearly from the two ends (108, 208) in the direction of the center. A mattress according to any one of the preceding claims, characterized in that the proportion of the stiffness of the core (101, 201) near the foot end (108, 208) to the stiffness near the center and near the head end (108',208') is as at least 3:4:3, and preferably as 1:5:3. A mattress according to any one of the preceding claims, characterized in that the mattress ins inversely symmetrical. A mattress according to any one of the preceding claims, characterized in that the core (101, 201) is provided, at least near the head end and/or the foot end, with hinge means.

Inventors: RIEKEN RENERIUS, RIEKEN, RENERIUS
Applicants: RECTICEL NEDERLAND BV, RECTICEL NEDERLAND B.V.
Application year: 1994
Main classification: A47C27
IPC codes: A47C27